System for combined transcutaneous blood gas monitoring and negative pressure wound treatment

ABSTRACT

A method and apparatus for the transcutaneous monitoring of blood gases generally comprises a blood gas data acquisition device, a vacuum source and a blood gas transducer unit. The blood gas transducer unit is adapted for application to a patient&#39;s skin and administration of a local vacuum at the area of patient application. It further comprises an electrochemical blood gas transducer, well known to those of ordinary skill in the art, which is disposed entirely within the local vacuum at the area of patient application. The vacuum source is placed in fluid communication with the blood gas transducer unit, through a hydrophobic membrane filter for safety purposes, in order to induce a condition of hyperperfusion in the locality of the electrochemical blood gas transducer. Under the control of a microcontroller, or equivalent means, the blood gas acquisition device is then utilized to capture a measure of skin surface oxygen or carbon dioxide pressure. The microcontroller can then utilize this measure to arrive at an estimate of arterial partial pressure of oxygen or carbon dioxide, accordingly. Because vacuum induced perfusion produces the requisite condition of hyperperfusion without local heating and, therefore, without acceleration of the local metabolic function, the present invention results in more accurate than previously available estimates of partial pressure blood gas pressures and does so while eliminating a significant risk for injury to the patient.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/085,321 filed Feb. 28, 2002 now U.S. Pat. No.6,856,821, which is acontinuation-in-part, of U.S. patent application Ser. No. 09/579,755,entitled “Transcutaneous Blood Gas Monitoring with Vacuum Pefusion,”filed on May 26, 2000, now abandoned which claims priority fromProvisional Application No. 60/136293, filed May 27, 1999.

FIELD OF THE INVENTION

The present invention relates to the monitoring of blood gases duringvacuum assisted wound healing. More particularly, the invention relatesto a method and system for the transcutaneous monitoring of blood gaseswherein said monitoring is enhanced by application of a vacuum pressurein the region of skin under evaluation, and during which negativepressure therapy is being applied to an adjacent or proximal wound site.

BACKGROUND OF THE INVENTION

Transcutaneous blood gas monitoring is known in the relevant arts as amethod by which measurements of skin-surface gas pressures may beutilized to estimate arterial partial pressures of the gas of interest.In particular, skin surface oxygen or carbon dioxide pressure PO₂ orPCO₂, respectively, is measured by a locally applied, electrochemicallybased device in order to develop an estimate of arterial partialpressure of oxygen or carbon dioxide P_(a)O₂ or P_(a)CO₂, respectively.The obtained estimate is then made available to the clinician as an aidfor the routine or emergency assessment of any of a variety of knowncardiopulmonary functions.

In practice, a condition of hyperperfusion is indicated in the region ofskin adjacent the applied device in order to enhance the flow ofarterial blood gases toward and through the skin surface. To date, thishyperperfusion condition has been established by local heating of theskin with an electrode in order to distend the arterial capillaries.Unfortunately, such local heating carries with it an increased risk fortissue injury—erythema, blisters, burns and skin tears being among thedocumented complications. In addition, some debate exists within the artas to whether the increased local metabolic rate concomitant theapplication of heat counteracts the intended perfusion effect. If so,false readings may result, which may ultimately lead to inappropriatetreatment of the patient.

The use of transcutaneous blood gas monitoring can be particularlyadvantageous when used in conjunction with negative pressure therapy forvacuum induced healing of open wounds or other tissue damage. Vacuuminduced healing of open wounds has recently been popularized by KineticConcepts, Inc. of San Antonio, Texas. by its commercially availableV.A.C.® product line. The vacuum induced healing process has beendescribed in commonly assigned U.S. Pat. No. 4,969,880 issued on Nov.13, 1990 to Zamierowski, as well as its continuations and continuationsin part, U.S. Pat. No. 5,100,396, issued on Mar. 31, 1992, U.S. Pat. No.5,261,893, issued Nov. 16,1993, and U.S. Pat. No. 5,527,293, issued Jun.18, 1996, the disclosures of which are incorporated herein by thisreference. Further improvements and modifications of the vacuum inducedhealing process are also described in U.S. Pat. No. 6071,267, issued onJun. 6, 2000 to Zamieroweki and U.S. Pat. Nos. 5,636,643 and 5,645,081issued to Argenta et al. on Jun. 10,1997 and Jul. 8, 1997 respectively,the disclosures of which are incorporated by reference as though fullyset forth herein. Additional improvements have also been described inU.S. Pat. No. 6,142,982, issued on Nov. 7. 2000 to Hunt et al.

The use of transcutaneous blood gas monitoring in conjunction withV.A.C.® therapy allows for monitoring of blood gases within and aroundthe wound bed. Blood gases can be an indicative factor of wound healingprogression. Crucial information can be ascertained as to theprogression of the wound without disturbing the wound dressing.

It is therefore a primary object of the present invention to improveover the prior art by providing a method and apparatus for thetranscutaneous monitoring of blood gases wherein local heating forhyperperfusion is eliminated, thereby eliminating a significant patienthazard and wherein the concomitant metabolic effects of local heatingare likewise eliminated, thereby reducing the likelihood formisdiagnosis leading to inappropriate treatment regimen.

Hyperperfusion through local heating also requires a prolonged warm upand stabilization time following electrode placement in order forequilibration and calibration of the electrochemical transducer. As aresult, operator time is generally wasted in the administration of atranscutaneous blood gas evaluation. Additionally, transcutaneous bloodgas monitors are either not available for emergency use or must be madeavailable with an operated in a standby mode. Such a standby moderequires additional hardware and generally shortens the electrodelifecycle.

It is therefore a further object of the present invention to improveover the prior art by providing a method and apparatus for thetranscutaneous monitoring of blood gases wherein the apparatus isavailable for full operation on short notice without requirement foradditional and/or lifecycle shortening hardware.

It is still a further object of the present invention to provide asystem and method that combines the advantages of a non-invasive bloodgas monitoring device with the effectiveness of negative pressuretherapy upon wounds, so as to further improve the efficacy of negativepressure therapy on the treatment of wounds and other tissue treatments.

Finally it is still a further object of the present invention to improveover the prior art by providing a method and apparatus for thetranscutaneous monitoring of blood gases wherein the above-describedobjects are implemented without sacrifice to patient safety or deviceefficacy, but wherein unnecessary hardware and software is nonethelessavoided, thereby conserving the ever more limited healthcare dollar.

SUMMARY OF THE INVENTION

In accordance with the foregoing objects, the present invention—a methodand system for the transcutaneous monitoring of blood gases and vacuumassisted wound closure-generally comprises a blood gas data acquisitiondevice, a vacuum source and a blood gas transducer unit. The blood gastransducer is adapted for application to a patient's skin andadministration of a local vacuum at the area of patient application. Itfurther comprises an electrochemical blood gas transducer, well known tothose of ordinary skill in the art, which is disposed entirely withinthe local vacuum at the area of patient application. The transducer mayalso be disposed within a wound site, or an area immediately adjacent awound site that is being treated by negative pressure therapy. The useof negative pressure therapy may include a porous, semi-rigid screenplaced within a wound bed, a cover for maintaining a negative pressurewithin the wound bed that is placed over the screen and wound bed, and avacuum source in fluid communication with the screen. Additionally, acanister may be disposed between the screen and vacuum source, for thecollection of fluids that may emanate from the wound during applicationof negative pressure by the vacuum source. A flexible tube or similardevice is used to communicate between the screen and vacuum source.

It is contemplated that the transducer may be incorporated within thescreen, or alternatively placed as a separate element below the screento be in direct contact with the wound bed, within a depression orcut-out of the screen, above the screen, or separate from the screen butimmediately adjacent the wound bed.

The blood gas transducer unit is in fluid communication with the vacuumsource through an interposed vacuum hose and in electrical communicationwith the blood gas data acquisition device through an interposedelectrical cable. The vacuum source, which comprises a vacuum pumpoperated by a pump motor is placed in fluid communication with the bloodgas transducer unit in order to induce a condition of hyperperfusion inthe locality of the electrochemical blood has transducer. Under thecontrol of the microcontroller, or equivalent means, the blood gas dataacquisition device is then utilized to capture this measure to arrive atan estimate of arterial partial pressure of oxygen or carbon dioxide,accordingly. Because vacuum induced perfusion produces the requisitecondition of hyperperfusion without local heating and, therefore,without acceleration of the local metabolic function, the presentinvention results in more accurate than previously available estimatesof partial blood gas pressures and does so while eliminating asignificant risk for injury to the patient.

The same vacuum source, or alternatively a second vacuum source, may beutilized to provide negative pressure at the wound site by communicatingwith the screen placed within the wound site, by means of a tube orsimilar device.

Because the application of vacuum perfusion to the patient presents atleast some risk for contamination of the vacuum source and blood gasdata acquisition device, the preferred embodiment of the presentinvention further comprises a transducer interface module particularlyadapted for the reduction or elimination of contamination risk.According to the invention, the transducer interface module comprises amale and female interface pair, wherein the male portion is adapted intothe female portion and thereby establishes communication between theblood gas transducer unit and the vacuum source and blood gas dataacquisition device.

In implementing the male plug, a hydrophobic membrane filter—known tothose of ordinary skill in the art—is interposed in the vacuum hose,thereby eliminating the opportunity for contaminants to pass from thepatient to the vacuum source or blood gas data acquisition device. Whilethe preferred embodiment of the present invention comprises a throw-awaymale plug, vacuum hose, electrical cable and blood gas transducer unit,those of ordinary skill in the art will recognize that each of thesecomponents can be made reusable with implementation of proper, knownsterilization techniques. In this latter case, the hydrophobic membranefilter is preferably replaceable.

Finally, many other features, objects and advantages of the presentinvention will be apparent to those of ordinary skill in the relevantarts, especially in light of the foregoing discussions and the followingdrawings and exemplary detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the invention will now bedescribed with reference to the drawings of certain preferredembodiments, which are intended to illustrate and not to limit theinvention, and wherein like reference numbers refer to like components,and in which:

FIG. 1 shows, in perspective view, the preferred embodiment of thetranscutaneous blood gas monitoring apparatus of the present invention,as employed with a human subject;

FIG. 2 shows, in schematic block diagram, details of the apparatus ofFIG. 1; and

FIG. 3 shows, in schematic block diagram, a transcutaneous blood gasmonitoring device utilized in conjunction with a negative pressuretherapy device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Although those of ordinary skill in the art will readily recognize manyalternative embodiments, especially in light of the illustrationsprovided herein, this detailed description is exemplary of the preferredembodiment of the present invention, the scope of which is limited onlyby the claims that may be drawn hereto.

Referring now to FIG. 1, the preferred embodiment of the transcutaneousblood gas monitoring system 10 of the present invention is shown togenerally comprise a blood gas data acquisition device 11, a vacuumsource 12 and a blood gas transducer unit 13. As shown in FIG. 1, theblood gas transducer unit 13 is adapted for application to a patient'sskin 14. In alternative embodiments, not shown, the blood gas transducermay be applied within a wound bed 30 or disposed within a screen 32placed within the wound bed 30. As will be better understood furtherherein, the blood gas transducer unit 13 is also adapted foradministration of a local vacuum at the area of the patient application.Finally, the blood gas transducer unit 13 comprises an electrochemicalblood gas transducer 15, well known to those of ordinary skill in theart, which is disposed entirely within the local vacuum at the area ofpatient application.

As also depicted in FIG. 1, the blood gas transducer unit 13 is in fluidcommunication with the vacuum source 12 through an interposed vacuumhose 16 and in electrical communication with the blood gas dataacquisition device 11 through an interposed electrical cable 17.Although those of ordinary skill in the art will recognize manysubstantial equivalents, the preferred embodiment of the presentinvention comprises a unitary hose and cable pair 18. Such a unitarypair 18 serves to reduce clutter in the patient care environment,thereby reducing the likelihood of either the hose 16 or cable 17becoming entangled with other tubes, cables or equipment. Further, andas will be better understood further herein, such a unitary pair 18 isespecially adapted for use with the preferred embodiment of the noveltransducer interface module 19 of the present invention.

According to the preferred embodiment of the present invention, in FIG.2, the vacuum source 12 comprises a vacuum pump 20 operated by a pumpmotor 21. Those of ordinary skill in the art, however, will recognizemany substantially equivalent embodiments for the vacuum source 12including, for example, a central hospital vacuum or suction source oran integral pump and motor. In any case, all such equivalents areconsidered within the scope of the invention, which requires only avacuum source 12 of the character otherwise described herein and whichis capable of providing suction in the range of about 50 mmHg through250 mmHg.

In operation, the vacuum source 12 is placed in fluid communication withthe blood gas transducer unit 13 in order to induce a condition ofhyperperfusion in the locality of the electrochemical blood gastransducer 15. Under the control of a microcontroller 22, or equivalentmeans, the blood gas data acquisition device 11 is then utilized tocapture a measure of skin surface oxygen and/or carbon dioxide pressure.The microcontroller 22 can then utilize this measure to arrive at anestimate of arterial partial pressure of oxygen or carbon dioxide,accordingly. Because vacuum induced perfusion produces the requisitecondition of hyperperfusion without local heating and, therefore,without acceleration of the local metabolic function, the presentinvention results in more accurate than previously available estimatesof partial blood gas pressures and does so while eliminating asignificant risk for injury to the patient.

Because the application of vacuum to the patient presents at least somerisk for contamination of the vacuum source 12 and blood gas dataacquisition device 11, the preferred embodiment of the present inventionfurther comprises a transducer interface module 19 particularly adaptedfor the reduction or elimination of contamination risk. According to theinvention, the transducer interface module 19 comprises a male 23 andfemale 24 interface pair, wherein the male portion 23 is adapted to pluginto the female portion 24 and thereby establish communication betweenthe blood gas transducer unit 13 and the vacuum source 12 and blood gasacquisition device 11.

In implementing the male plug 23, a hydrophobic membrane filter 25—knownto those of ordinary skill in the art—is interposed in the vacuum hose16, thereby eliminating the opportunity for contaminants to pass fromthe patient 14 to the vacuum source 12 or blood gas data acquisitiondevice 11. While the preferred embodiment of the present inventioncomprises a throw-away male plug 23, vacuum hose 16, electrical cable 17and blood gas transducer unit 13, those of ordinary skill in the artwill recognize that each of these components can be made reusable withimplementation of proper, known sterilization techniques. In this lattercase, the hydrophobic membrane filter 25 is preferably replaceable.

Referring now to FIG. 3, a collection canister 34 may be interposedbetween the vacuum source 12 and the screen 32. As suction is applied,fluids may be drawn from the wound 30 and collected in the canister 34.A common vacuum source 12 may be utilized to provide vacuum perfusion tothe blood gas transducer 13 and negative pressure to the wound site 30.A seal 36 is adhered over the screen 32 in order to maintain negativepressure within the wound site 30. The seal 36 may be comprised of anelastomeric material. The screen 32 is preferably comprised ofpoly-vinyl alcohol foam, or alternatively a polyurethane porous sheet.It is to be understood that any semi-rigid and porous material may beutilized as a screen 32 within the wound bed 30. The tube 16 may be indirect fluid communication with the screen 32 (not shown), or connectedto an adapter 38 that is adhered over an opening 40 in the seal 36. Itis preferable that the tube 16 is bifurcated at a position between thevacuum source 12 and the canister 34 so that fluids being drawn from thewound site 30 do not interfere with the vacuum perfusion of the bloodgas transducer 13.

In an alternate embodiment, not shown, a separate vacuum source may beutilized to provide negative pressure to the wound site 30 and anothervacuum source utilized to provide vacuum perfusion to the blood gastransducer 13.

While the foregoing description is exemplary of the preferred embodimentof the present invention, those of ordinary skill in the relevant artswill recognize the many variations, alterations, modifications,substitutions and the like as are readily possible, especially in lightof this description and the accompanying drawings. For example, in FIG.1, a membrane or other like switch pad 26 may be implemented for usercontrol of the transcutaneous blood gas monitor 10 and/or a display,printer or other output device 27 may be provided for monitoring and/orrecording of estimated partial pressures. Likewise, in FIG. 2. apressure transducer 28 may be, and preferably is, provided formonitoring and control of the vacuum applied to the patient's skin 14.In any case, because the scope of the present invention is much broaderthan any particular embodiment, the foregoing detailed descriptionshould not be construed as a limitation of the scope of the presentinvention, which is limited only by the claims that may be drawn hereto.What is claimed is:

1. A transcutaneous blood gas monitoring device particularly suited forapplication to a site on a patient's skin under a local vacuum,comprising: a non-invasive blood gas data acquisition device, thenon-invasive blood gas data acquisition device adapted to measure skinsurface oxygen and carbon dioxide pressure; a vacuum source in fluidcommunication with a wound site in proximity to the site on thepatient's skin for applying a negative pressure to the wound site; anelectrochemical blood gas transducer unit in fluid communication withsaid vacuum source; a transducer interface module communicating betweenthe electrochemical blood gas transducer unit, the vacuum source and thenon-invasive blood gas data acquisition device and adapted to reduce oreliminate contamination; and a screen formed to fit within said woundsite.
 2. The transcutaneous blood gas monitoring device of claim 1,wherein the vacuum source is in fluid communication with theelectrochemical blood gas transducer unit through an interposed vacuumhose.
 3. The transcutaneous blood gas monitoring device of claim 2,wherein the electrochemical blood gas transducer unit is in electricalcommunication with the non-invasive blood gas data acquisition devicethrough an interposed electrical cable.
 4. The transcutaneous blood gasmonitoring device of claim 3, wherein the interposed vacuum hose and theinterposed electrical cable comprise a unitary hose and cable pair forreduction of entanglement with other tubes, cables or equipment.
 5. Thetranscutaneous blood gas monitoring device of claim 4, furthercomprising a hydrophobic membrane filter interposed in the interposedvacuum hose.
 6. The transcutaneous blood gas monitoring device of claim5, wherein the hydrophobic membrane filter is disposable.
 7. Thetranscutaneous blood gas monitoring device of claim 3, wherein thenon-invasive blood gas data acquisition device monitors healing of thewound site.
 8. The transcutaneous blood gas monitoring device of claim3, further comprising: a seal for maintaining the negative pressurewithin said wound site during application of negative pressure.
 9. Thetranscutaneous blood gas monitoring device of claim 3, furthercomprising a collection canister interposed between the vacuum sourceand the screen.
 10. The transcutaneous blood gas monitoring device ofclaim 9, wherein the interposed vacuum hose is bifurcated at a positionbetween the vacuum source and the collection canister to prevent fluidsdrawn from the wound site from interfering with the electrochemicalblood gas transducer unit.
 11. The transcutaneous blood gas monitoringdevice of claim 3, further comprising a controller for governing actionsof said non-invasive blood gas data acquisition device.
 12. Thetranscutaneous blood gas monitoring device of claim 1, wherein thetransducer interface module comprises a male and female interface pair,wherein the male interface is adapted to plug into the female interfaceand establish communication between the electrochemical blood gastransducer unit, the vacuum source and the non-invasive blood gasacquisition device.
 13. The transcutaneous blood gas monitoring deviceof claim 1, wherein the vacuum source comprises a vacuum pump operatedby a pump motor.
 14. The transcutaneous blood gas monitoring device ofclaim 1, wherein the electrochemical blood gas transducer unit isincorporated within the screen.
 15. The transcutaneous blood gasmonitoring device of claim 1, wherein the screen is in fluidcommunication with the vacuum source.
 16. The transcutaneous blood gasmonitoring device of claim 1, further comprising a second vacuum sourceadapted to provide negative pressure at the wound site by communicatingwith the screen.
 17. The transcutaneous blood gas monitoring device ofclaim 1, wherein the vacuum source is capable of providing suction in arange of about 50 mmHg to about 250 mmHg.
 18. A transcutaneous blood gasmonitoring device particularly suited for application to a site on apatient's skin under a local vacuum, comprising: a non-invasive bloodgas data acquisition device; a vacuum source in fluid communication witha wound site in proximity to the site on the patient's skin for applyinga negative pressure to the wound site; an electrochemical blood gastransducer unit in fluid communication with said vacuum source, theelectrochemical blood gas transducer unit in electrical communicationwith the non-invasive blood gas data acquisition device through aninterposed electrical cable, and the vacuum source in fluidcommunication with the electrochemical blood gas transducer unit throughan interposed vacuum hose; a transducer interface module communicatingbetween the electrochemical blood gas transducer unit, the vacuum sourceand the non-invasive blood gas data acquisition device and adapted toreduce or eliminate contamination; a screen formed to fit within saidwound site; and a collection canister interposed between the vacuumsource and the screen, wherein the interposed vacuum hose is bifurcatedat a position between the vacuum source and the collection canister toprevent fluids drawn from the wound site from interfering with theelectrochemical blood gas transducer unit.
 19. The transcutaneous bloodgas monitoring device of claim 18, wherein the interposed vacuum hoseand the interposed electrical cable comprise a unitary hose and cablepair for reduction of entanglement with other tubes, cables orequipment.
 20. The transcutaneous blood gas monitoring device of claim19, further comprising a hydrophobic membrane filter interposed in theinterposed vacuum hose.
 21. The transcutaneous blood gas monitoringdevice of claim 20, wherein the hydrophobic membrane filter isdisposable.
 22. The transcutaneous blood gas monitoring device of claim18, wherein the non-invasive blood gas data acquisition device monitorshealing of the wound site.
 23. The transcutaneous blood gas monitoringdevice of claim 18, further comprising: a seal for maintaining thenegative pressure within said wound site during application of negativepressure.
 24. The transcutaneous blood gas monitoring device of claim18, further comprising a controller for governing actions of saidnon-invasive blood gas data acquisition device.
 25. The transcutaneousblood gas monitoring device of claim 18, wherein the transducerinterface module comprises a male and female interface pair, wherein themale interface is adapted to plug into the female interface andestablish communication between the electrochemical blood gas transducerunit, the vacuum source and the non-invasive blood gas acquisitiondevice.
 26. The transcutaneous blood gas monitoring device of claim 18,wherein the vacuum source comprises a vacuum pump operated by a pumpmotor.
 27. The transcutaneous blood gas monitoring device of claim 18,wherein the electrochemical blood gas transducer unit is incorporatedwithin the screen.
 28. The transcutaneous blood gas monitoring device ofclaim 18, wherein the screen is in fluid communication with the vacuumsource.
 29. The transcutaneous blood gas monitoring device of claim 18,further comprising a second vacuum source adapted to provide negativepressure at the wound site by communicating with the screen.
 30. Thetranscutaneous blood gas monitoring device of claim 18, wherein thenon-invasive blood gas data acquisition device is adapted to measureskin surface oxygen and carbon dioxide pressure.
 31. The transcutaneousblood gas monitoring device of claim 18, wherein the vacuum source iscapable of providing suction in a range of about 50 mmHg to about 250mmHg.